1. Field of the Invention
The present invention relates to a semiconductor die package that may be mounted to a printed circuit board in both horizontal and upright configurations and, more particularly, to a semiconductor die package that houses a logic die and a sensor die and that provides a stable and durable surface mounting connection to a printed circuit board in both horizontal and upright configurations.
2. Description of the Related Art
A semiconductor die or chip is an electrical component on which a microcircuit is built. The microcircuits can be interconnected together on the printed circuit board to form larger electrical circuits for use in radios, televisions, compact disk players, and computers, to name just a few. Because the semiconductor die is fragile, it is encased in a semiconductor die package to protect it from the environment. Therefore, if one were to look inside an electronic device, such as a computer or a compact disk player, one would see one or more printed circuit boards on which semiconductor die packages are mounted and electrically interconnected.
The semiconductor die package includes a housing that holds the semiconductor die and conductive leads or pins that extend from the bottom or sides of the housing. The conductive leads are electrically connected to the semiconductor die within the housing. The outside ends of the leads are soldered to conductive paths on the printed circuit board. This secures the semiconductor die package to the printed circuit board and permits electrical signals to pass between the semiconductor die and other components on the printed circuit board.
In a conventional semiconductor die package, a housing holds the semiconductor die such that the active surface of the semiconductor die, i.e., the surface on which the microcircuit is built, faces away from a printed circuit board. However, it is also known to use a flip-chip arrangement, in which the semiconductor die is held in the housing so that the active surface of the semiconductor die faces the printed circuit board. In both cases, the active surface of the semiconductor die is held horizontal to the surface of the printed circuit board when the semiconductor die package is mounted to the printed circuit board.
Conductive leads extending from the bottom of the package housing are typically arranged in rows and columns. A pin grid array (PGA) is an example of this type of package. The package mounts to the printed circuit board in a horizontal configuration so that the active surface of the semiconductor die and the bottom of the package housing are parallel to the surface of the printed circuit board. Each conductive lead of the array inserts into a preformed plated-through-hole (PTH) in the printed circuit board to make an electrical connection.
Conductive leads that extend from the sides of the package housing are typically bent downward toward the printed circuit board. This enables the conductive leads to make electrical contact with the printed circuit board when the package is mounted to the printed circuit board in a horizontal configuration. The conductive leads usually extend from two or four sides of the package. Examples of these types of packages are the two-sided dual in-line package (DIP) and the four-sided quad flat package (QFP). Dual in-line packages use plated-through-hole connections to mount to the printed circuit board. Quad flat packages are surface mounted by soldering the package leads to conductive pads on the surface of the printed circuit board. Generally, surface mounting is preferred over plated-through-hole mounting for a variety of reasons which will not be discussed in detail here.
Some packages are designed to mount in an upright configuration such that the semiconductor die is on edge with respect to the surface of the printed circuit board. Examples of such packages are the single in-line package (SIP) and the zig-zag in-line package (ZIP). Both the single in-line package and the zig-zag in-line package having long leads extending from one side of the package and mount to printed circuit boards using plated-through-hole technology.
In certain applications, the ability to mount the semiconductor package either in the horizontal configuration or in an upright configuration is desirable. For example, some semiconductor dies operate as sensors to generate signals as a function of the direction in which they are held. One such semiconductor sensor is used to trigger inflation of a car's air bag when a rapid deceleration is sensed. Conventional packages are not adapted to be mounted both in horizontal and upright configurations. For example, a pin grid array has a two dimensional array of leads extending from the bottom of the housing and dual in-line packages and quad flat packages have electrically-active leads on multiple sides. Mounting such packages in an upright configuration would prevent some of the leads from contacting the printed circuit board. Moreover, the leads lack the strength and rigidity to establish a stable connection to the printed circuit board in an upright configuration. The leads could bend or break.
The durability of the connection between the semiconductor die package and the printed circuit board is critical in many applications. For example, packages that house semiconductor sensors are often used where environmental conditions are harsh, for example, in automobiles and airplanes. The connection between the package and the printed circuit board must endure high levels of stress and vibration and exposure to weather, dust, and dirt. Durability is a function, in part, of the mounting stability of the semiconductor die package on the printed circuit board. Therefore, the semiconductor package must be capable of providing a stable and durable connection to the printed circuit board in both horizontal and upright configurations.
One solution to this problem is to attach an extension or adaptor board at a right angle to the main printed circuit board. For example, a connector can be used to electrically connect the extension board to the main printed circuit board. The semiconductor package then can be mounted to the extension board in a configuration that is horizontal to the extension board, but upright with respect to the main circuit board. However, the use of extension boards complicates manufacture and drives up the cost. Therefore, there is a need for a durable and economical semiconductor die package that can mount to a printed circuit board both in horizontal and vertical configurations.